1. Field of the Invention
The embodiments herein generally relate to the field of electrical circuitry, and more particularly to a circuit capable of switching an amplified AC signal to any one of several transducers.
2. Description of the Related Art
Military personnel are often trained using hostile environment simulators. An example of such as simulator is an array of strategically spaced targets representing hostile fire or the enemy, etc. In order to best create a battlefield scenario sound systems are employed in such simulators to recreate battlefield noises in order to train military personnel. Conventionally, this sound system has included speakers arranged in various locations, some of which are isolated from one another due to the wide-spaced layout of the simulators. As such, each speaker is required to be powered by its own amplifier. This is because conventional switches cannot handle powered AC signals, therefore the signal would have to be amplified at each individual speaker. Such a setup is not only unduly expensive, but also requires significant resources for maintenance of each speaker/amplifier unit. Moreover, it has been virtually impossible to design a system, which can easily turn on or off a particular speaker so that there is no sound distortion emanating from the other speakers in the simulator. Recent simulator designs have required the capability of switching moderately powered AC signals.
A HEXFET®, available from International Rectifier, California, USA, is capable of handling higher currents and voltages better than a standard FET. To date, most of the hexagonal cell field effect transistors (HEXFET) applications for switching and power handling capabilities are involved with motor controls. Motor controls are DC power applications that are easily handled by power HEXFETs and require no special or unique circuitry. Conventionally, voltage is applied to the gate of the HEXFET, which turns the HEXFET on, supplying DC power to the motor. Switching of powered AC signals presents quit a different and more difficult problem. With an AC signal placed on the drain of the HEXFET, the HEXFET can be turned on inadvertently depending on the polarity and magnitude of the powered AC signal. For example if +5 volts is required to turn on a p-channel HEXFET and the gate has 0 volts applied to it, if the AC signal on the drain transitions to −5 volts, then the relative gate-drain voltage will be +5 volts and the HEXFET will turn on. This may not be a desirable effect in instances when it is not required for the HEXFET to be turned on, but does so nonetheless. Moreover, for control of a powered AC signal where complete isolation and total mitigation of the signal is required this is an undesirable effect.
Currently, there are no available systems that are capable of switching on/off high-powered acoustic signals. Most conventional switches are designed for DC TTL (transistor-transistor logic) level signals only. Moreover, most switches capable of handling power are for motor control only. As such, these conventional switches are not designed to handle AC or transient signals above 60 Hz.
Therefore, due to the limitations of conventional switching circuits there is a need for a switching circuit, which includes mitigation capabilities to handle voltage transients that could inadvertently turn a HEXFET on. Furthermore, there is a need for a circuit, which can accommodate high powered and high-speed AC signals.